1. Field of Invention
The invention relates to optical fiber. More particularly, the invention relates to systems and methods for color-coating optical fiber.
2. Description of Related Art
Optical fibers are thin strands of glass or plastic capable of transmitting optical signals containing relatively large amounts of information over long distances with relatively low attenuation. Optical fibers typically are made by heating and drawing a portion of an optical preform comprising a refractive core surrounded by a protective cladding made of glass or other suitable material. The drawn optical fiber then is protected further by applying one or more clear coating layers made of ultraviolet (UV)-cured or other suitable material. Typically, optical fiber is coated with a first or primary coating layer and a second or secondary coating layer.
Often, to aid in future identification and discrimination of optical fibers, coated optical fibers are colored by coating or top-coating the outer coating layer with a UV-curable ink having one of a plurality of colors, e.g., 12 or more colors. To save time and cost, some fiber manufacturers attempt to coat and color the optical fiber in a single step, i.e., to color the optical fiber during the coating step. See, e.g., U.S. Pat. Nos. 5,330,786; 6,317,553; and 6,321,014. In this manner, a pre-colored coating material is applied to the optical fiber. Typically, the pre-colored coating material is a conventional secondary coating pre-mixed with a color concentrate.
However, such conventional coloring during draw techniques have disadvantages. For example, in conventional coloring during draw arrangements, changing colors requires replacing the ink drum with a different ink drum and purging all the lines between the drum and the coating die. Also, manufacturing colorless optical fiber once a coloring-during-draw arrangement has been set up involves changing the ink drum and purging the lines. Furthermore, if there is not enough ink in the existing drum to coat the fiber drawn from an entire preform, the ink drum must be discarded.
Accordingly, it would be desirable to have available a system and method for coloring optical fiber during draw that overcomes the disadvantages of many conventional coloring during draw arrangements.